Addition of TPA center dot Cl (TPA: tetra-n-propylammonium) to a reaction mixture of H2WO4, H2O2, and HCl gave a novel all-inorganic mononuclear chloro oxo diperoxotungstate, TPA-[WOCl(O-2)(2)(H2O)] (I), which was characterized by X-ray crystallography, elemental analysis, and IR, Raman, UV-vis, O-17 and (WNMR)-W-183 spectroscopies, and CSI-MS. Compound I acted as a good precursor for the high-yield synthesis of an active protonated tetranuclear peroxotungstate, TPA(3)[H-{W2O2(O-2)(4)(mu-O)}(2)].